Forge furnace



2 Sheets-Sheet l c. o. KNIERIM FORGE FURNAGE Dec. 24, 1957 Filed Dec. 2,195s CARL o. msnm ATTORNEYS Dec; 24, .1957

Filed Dec. 2, 1953 c. o. KNIERIM 2,817,507

FORGE FURNACE 2 Sheets-Sheet 2 INVENTOR. KNIERIM nited States PatentFORGE FURNACE Carl 0. Knierim, Cleveland Heights, Ohio, assignor to TheGas Machinery Company, Cleveland, Ohio, a corporation of OhioApplication December 2, 1953, Serial No. 395,808

s claims. (ci. 263-37) The present invention relates to furnaces forheating metal billets to forging temperatures, i. e., temperatures aboveabout 2000 F. and more particularly to a furnace which providessubstantially uniform heating of the billet and more efficient use ofthe heat supplied to the furnace.

In heating metal billets to forging temperatures, particularly where thebillets are directly exposed to the combustion gases which heat thefurnace, the surfaces of the billets become scaled due to oxidation. Thescale represents a metal loss of from 3% to 5% of the billet and, if notremoved before the forging operation, seriously reduces the life of theforging dies.

To reduce the disadvantages due to scaling, attempts have been made toheat the billets in an inert atmosphere, i. e., in direct contact with anon-oxidizing or reducing atmosphere, the billets being heatedindirectly by the combustion gases.

The present invention provides an improved furnace for heating billetsin an inert or non-oxidizing atmosphere.

According to this invention, the enclosed passage for the billets has aninternal cross-section which conforms, in general, to the cross-sectionof the billet and is only slightly larger than the billet. By making thepassageways only slightly larger than the billet and of the same generalcross-sectional shape, a compactness is obtained which provides severaladvantages over the furnaces of the prior art. The number of passagewaysin a particular furnace may be increased to the maximum, thus increasingthe output of the furnace. The volume of inert gas required in thepassageways is reduced to a minimum, and the distance from the innerwalls of the passageway to the billet being heated is short andsubstantially uniform, thus providing substantially uniform heating ofthe billet on all sides.

The fact that a film of carbon from the inert gas is de-v posited on thesurface of the billet also protects the same from oxidation in transitfrom furnace to the press.

All of these advantages contribute to a far more ei cient operation thanwas possible heretofore, not only by increasing the overalloutput of thefurnace, but also by more eflicient utilization of the heat and moreuniform heating of the billets and by eliminating scaling. In addition,the required amount of non-oxidizing atmosphere is reduced to a minimum.

The present invention will be described with reference to theaccompanying drawings, in which:

Figure l is a longitudinal vertical cross-section of a furnace accordingto the present invention taken along line 1-1 of Figure 2;

Figure 2 is a transverse vertical cross-section of the furnace shown inFigure 1, taken along line 2-2 thereof; and

Figures 3, 4 and S illustrate in vertical cross-section modifications ofthe passageways shown in Figure 2.

Referring to Figures 1 and 2, the furnace comprises a conventional steelframework which supports refractory walls 11, a refractory floor 12 anda refractory roof 13.

A plurality of burners 14, for supplying hot combustion gases, areprovided in the walls 11. Flues 15 for venting the combustion gases fromthe furnace may be provided in one of the side Walls 11.

Along the length of the furnace are provided refractory supports 16 onwhich are mounted the enclosed passageways indicated generally at 17.Although six passageways have been shown, it will be understood that anynumber of such passageways may be provided depending upon the relativesizes thereof and of the furnace and the expected output of the furnace.

At the end of the furnace where the billets are discharged, there areprovided downwardly sloping passages 18 associated with each enclosedpassageway 17, through which the billets slide after having been heatedto the desired temperature. The discharged billets drop onto a conveyor19 to be transported to a forging press or other metal treatingoperation. At the lower ends of passages 18 are provided doors 20 whichare normally closed but are automatically opened by the billets topermit them to be discharged as will be described more fully hereafter.

At the other and charging end of the furnace, and associated with eachenclosed passageway 17, a plurality of hoppers or magazines 21 (only onebeing shown) are provided for containing a supply of billets to beheated. At the base of each of the hoppers 21 a pushing device orplunger 22 is provided for intermittently pushing the bottom billetsfrom the magazine 21 into the associated passageway 17 for the heatingoperation. The billets progress intermittently through the passageway 17as additional billets are introduced thereinto by the pushing device 22until they reach the sloping passage 18 when they will slide down saidpassage and through the door 20 onto the conveyor 19.

The passageways 17 may take any of the illustrative forms shown in thecross-section in Figures 2, 3, 4 and 5 and may comprise refractory bases23 Which rest on the supports 16 in spaced parallel arrangement. As willbe seen in the various figures, the bases 23 may have different shapesfor accommodating different types of covers or hoods 24 and differenttypes of billets.

In Figure 2, each base 23 has a longitudinal raised center section 25,of somewhat greater width than the prismatic billet shown in Figures 1and 2, and longitudinal shoulders 26 on which are disposed hoods 24. Thecrosssectional shape of the hoods 24 in Figure 2 'correspond in generalto the cross-sectional shape of the billets 27, so that the billets aresubjected to substantiaily uniform ra diant heat.

In Figure 3 the cover or hood 24 consists of a tube which is supportedon the base 23 as shown. In the present case, the term hood or cover isintended to include a tube as shown in Figure 3 as Well as the coversshown in Figures 2, 4 and 5. As shown in Figure 3, the billet 21 has acylindrical shape and is subjected to substantially uniform radiant heatas mentioned above.

Figure 4 illustrates another form of passageway which can be used withcylindrical billets. The hood 24 is similar to that shown in Figure 2,except that it has a curved top which conforms in general to thecross-section of the billet. The raised portion of the base 23 isprovided with a curved surface to conform generally to the shape of thebillet.

In Figure 5, the base member 23 is provided with a pair of steel tubes28 which extend longitudinally along the base and are spaced apart toprovide a pair of skids for either prismatic billets or cylindricalbillets, both shapes being shown in phantom outline. The tubes 28 arewater-cooled so as to prevent any damage thereto by the hightemperatures used in forge furnaces. Since the tubes essentially provideonly line contact with the billets, it will be seen that the coolingeffect of these tubes on the billet will be negligible. The hood 24, inthis modification, is curved, as shown in Figure 5, and While theprismatic billets are subjected to radiant heat which is not quite souniform as when cylindrical billets arc heated, they are, nevertheless,very uniformly heated. This moditication has the advantage of beingsuitable for use with either type of billet, while the passageways shownin Figures 2, 3 and 4 are generally only suitable for use with one typeof billet, as shown.

It will, of course, be understood that any furnace may be provided witha plurality of the same type or different types of passageways,depending on requirements.

Referring now to Figure 1, an inlet 29 is provided near the. dischargeend of sloping passageway 18 for the introduction of non-oxidizing orreducing gas. The gas moves through the passageway, counter-current tothe movement of the billets and is vented through exit pipe 30, whichcommunicates with the inlet end of the passagewayy 17. A conventionalspring-mounted closure 31 is provided at the end of the passageway topermit expansion thereof when being heated up.

lf desired, the gas may ow concurrently through the passageway 17instead of counter-currently. In such a case, of course, an inletsimilar to inlet 29 would be provided in the passageway 17 adjacent exitpipe 30, and an exit pipe similar to pipe 30 would communicate withpassage .1S adjacent the door 20.

Passageway 17 has a co-linear extension 32, which terminates at the door33 to facilitate cleaning of the passageway when necessary.

The inert gas in the passageways 17 is maintained at a pressure slightlyabove that of the combustion gases so as to prevent any leakage of thelatter into the passageways.

Even though the sections of the hoods 24 and bases 23 usually only abutone another, the abutting surfaces have such smoothness that a veryecient gas seal is obtained. Furthermore, the spring closure 31 tends tokeep the sections of the hoods and bases under compression.

Various types of atmosphere may be used within the passageways, but ithas been found that hydrocarbons may be used satisfactorily, such as rawpropane. Other non-oxidizing gases are Well-known in the art.

Although the present invention has been described with particularreference to the apparatus shown in the drawings, it will be understoodthat various modifications of the present furnace will occur to thoseskilled in the art, and it is intended that such modifications as comewithin the scope of the appended claims be covered thereby.

What I claim is:

1. A furnace for heating elongated billets to forging emperatures whilepushing them one after another in endto-end relationship through aheating zone of the furnace, said furnace comprising refractory sidewall, end wall, roof, and floor portions dening a combustion chamber, atleast one generally tubular assembly of small exterior cross-sectionrelative to that of said combustion chamber and longitudinally uniforminterior cross-section, said assembly extending substantiallyhorizontally and longitudinally through the furnace between the end wallportions thereof intermediate and spaced from said roof and floorportions, said assembly, within said combustion chamber, enclosing anelongated passageway constituting said heating zone to exclude therefromgases present in said combustion chamber, exterior openings axially intothe ends of said assembly, means operative for intermittentlyintroducing billets through one of said openings into said assembly formovement axially therethrough and through said heating zone, meansnormally closing the opposite end of said assembly and operable topermit withdrawal of heated billets intermittently as they arriveadjacent said opposite end, and means for introducing and burning acombustible fuel in said combustion chamber about said assembly, eachsuch assembly comprising a plurality of separable, elongated, refractorybase members disposed in end-toend co-linear engagement from one end ofthe assembly to the other, a substantially co-extensive plurality ofsimilarly disposed, separable, elongated, refractory cover sections4resting on said base sections and defining said uniform interiorcross-section of said tubular assembly above said base members, wherebythe interior cross-section of said tubular assembly may be adapted toclosely surround and generally conform to any given crosssection of aseries of billets to be pushed therethrough merely by selecting coversections of appropriate crosssectional size and configuration, each suchtubular assembly being abutted endwise against an adjacent end wallportion of the furnace and the opposite end of the assembly projectinginto an opening in an opposite end wall portion of the furnace, and saidfurnace additionally comprising means for applying a yielding forceagainst said opposite end of each such assembly to hold the separablesections thereof in end-wise compression between one another and the endWall portion abutted by one end of the assembly, whereby gas perviousgaps between the separable sections are minimized, and means forintroducing a desired non-oxidizing gas under pressure into one end ofsaid assembly and exhausting it from the opposite end thereof tomaintain a pressure of said gas in the assembly above the gas pressurein said combustion chamber about the assembly for preventing leakage ofcombustion products from the combustion chamber into said heating zone.

2. A furnace according to claim 1 in which said base members areprovided with longitudinally extending raised center sections fordirectly supporting billets and longitudinally extending shoulders onopposite sides of said center sections for supporting said coversections.

3. A furnace according to claim 1 including a pair of spaced, parallel,skids supported on said base members and extending longitudinallythereof to support billets moving through the furnace.

4. A furnace accordingto claim 1 in which said cover sections aresubstantially semi-circular in transverse crosssection.

5. A furnace according to claim l in which said cover sections aresubstantially U-shaped in transverse crosssection.

References Cited in the file of this patent UNITED STATES PATENTS1,508,135 Blount et al. Sept. 9, 1924 1,692,614 Bissell Nov. 20, 19281,710,870 Forse Apr. 30, 1929 1,756,584 Cope Apr. 29, 1930 2,022,649 Corriston Dec. 3, 1935 2,103,234 Clauss et al Dec. 28, 1937 2,472,497Stookey June 7, 1949 2,485,782 Schweitzer Oct. 25, 1949

